i realized my post was misworded after your comment and yes thats what i meant. i was writing this while stuck in a parking lot trying to get a quick fix to get home and do a repair, so i was a little distraught not having a parts guide to determine what the hose was responsible for. i ended up clamping it for 5 min driving time and it worked fine.
btw, the expansion tank is fine, it was just this little nipple that mysteriously broke off.